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There are several important questions that need to be

answered when attempting to identify a pathologic rhythm.

First, determine the hemodynamic stability of the patient.

Look for any signs of hypoperfusion, including systemic

hypotension, cardiac chest pain, pronounced diaphoresis,

altered mental status (AMS), or congestive heart failure.

Second, quantify the rate of the dysrhythmia and classify as

normal, slow, or fast. Third, identify the morphology of the

rhythm (eg, narrow vs wide complex QRS). Next, determine whether the observed dysrhythmia is irregular or

regular in cadence. Finally, assess for any evidence of an AV

conduction block. AV blocks are divided into first, second,

and third degrees based on the PR interval and the cardiac

rhythm.

Narrow rhythms:

• Fast: Atrial fibrillation, atrial flutter, SVT

• Slow: Sinus bradycardia, j unctional escape rhythm

Wide rhythms:

• Fast: Ventricular tachycardia (VT), AF, or flutter with

aberrant conduction

• Slow: Hyperkalemia, third-degree (complete) heart

block

CLINICAL PRESENTATION

� History

Unstable patients may be too altered to offer any meaningful history. Employ any available friends, family, and

emergency medical service personal for possible critical

details. Unstable patients require immediate intervention,

and time should not be wasted on an excessively detailed

history. In stable patients, ask about any previous episodes, current medications, illicit drug use, and the timing of symptom onset. Inquire about a history of any

underlying structural anomalies (eg, Wolf-ParkinsonWhite syndrome [WPW] ), as this will help guide therapy

(Figure 1 6-1).

Finally, ascertain about past medical history. Although

sinus bradycardia is a common finding in healthy adults,

older patients with underlying coronary artery disease

( CAD) and slow heart rates often have a pathologic

source for their bradydysrhythmia ( eg, inferior wall isch ­

emia, electrolyte abnormalities, or pharmacologic side

effects). Similarly, although sinus tachycardia often

accompanies conditions with increased sympathetic

tone (eg, exercise, fever, cocaine use), older patients with

a history of CAD, valvulopathy, or underlying pulmo ­

nary disease often have a pathologic source for their

tachydysrhythmia.

� Physical Examination

Evaluate the patient's hemodynamic stability. Always note

the triage vital signs and repeat frequently. Carefully palpate peripheral pulses to determine whether they corre ­

spond with the dysrhythmia displayed on the cardiac

monitor. Assess for signs of end-organ hypoperfusion,

including detailed cardiovascular (weak peripheral pulses),

pulmonary (rales), and neurologic (AMS) examinations.

Check for additional findings that may help identify the

source of the dysrhythmia. Patients with thyrotoxicosis

may have a goiter, peripheral tremor, and ocular proptosis.

Discovering a dialysis catheter or palpable AV fistula

should prompt concern for hyperkalemia. A sternotomy

scar should prompt concern for either acute coronary syndrome (ACS) or valvular disease as the precipitating

source.